This invention relates to the field of satellites, and in particular to a dispenser for deploying canisterized satellites, such as CubeSat, from a larger spacecraft, such as a launch vehicle, a shuttle, or a space station.
California Polytechnic State University (“Cal Poly”) initiated the CubeSat concept in 1999, to enable universities to perform space science and exploration. A basic CubeSat (“1U”) is a 10 cm1 cube (one liter in volume) having a mass of not more than 1.33 kg. Other common sizes are available, including a “2U” that is 20 cm×10 cm×10 cm, and a “3U” that is 30 cm×10 cm×10 cm. Other sizes, such as a “6U” (30 cm×10 cm×20 cm), “12U” (30 cm×20 cm×20 cm), and “27U” (30 cm×30 cm×30 cm), have also been proposed. 1 Dimensions cited herein are ‘nominal’.
In a typical university scenario, students build a CubeSat to perform a particular task in space, then coordinate with launch service providers to obtain “space-available” allocation on a delivery spacecraft, such as a launch vehicle, a shuttle, or a space station. Because the CubeSats are small, they may often be placed in the spaces between the larger payloads in the delivery spacecraft.
To deploy a CubeSat in space, a dispensing device is used to ‘push’ the CubeSat away from the delivery spacecraft. This dispensing device is also used to transport the CubeSat and to secure it to the delivery spacecraft. Current dispensing devices include the “P-Pod” (Poly's Pico-satellite Orbital Deployer), designed by Cal Poly, and the ISIPOD deployer, designed by ISIS (Innovative Solutions In Space). The P-Pod deployer accommodates a “3U” CubeSat, or, equivalently, three “1U” CubeSats, or, one “1U” CubeSat and one “2U” CubeSat”. The ISIPOD is available in a variety of sizes.
FIGS. 1A-1B illustrate a conventional P-Pod device 100. A spring-loaded door 110 secures the CubeSat(s) within the P-Pod. Upon receipt of a deployment signal, a release mechanism 120 releases the door 110, which swings open at least 90 degrees.
Within the P-Pod, a coil spring 160 is situated behind a push-plate 150. As the CubeSats are inserted into the P-Pod, the coil spring 160 is compressed. After the CubeSats are inserted into the P-Pod, the door 110 is latched, holding the coil spring 160 in compression. Access doors 130 provide access to the inserted CubeSats, and may be used, for example, to charge batteries or run diagnostic tests. Mounting brackets 180 are used to secure the P-Pod to the delivery spacecraft.
Release of the door 110 allows the coil spring 160 to push the push-plate 150 toward the door 110, resulting in the discharge of the CubeSats from the P-Pod. Four teflon coated guide rails 170 are used to facilitate a lateral discharge of the CubeSats. Nominally, the CubeSats exit the P-Pod at about 1.6 m/sec; different sized coil springs 160 may be used to increase or decrease this exit velocity. Four spring plungers (not illustrated) in the rear of the P-Pod supplement the coil spring 160.
FIG. 2 illustrates a conventional “1U” CubeSat 200. The “2U” and “3U” CubeSats have the same dimensions in the illustrated ‘x’ and ‘y’ directions, and extend further in the ‘z’ direction by a multiple of two and three, respectively.
Each CubeSat, regardless of size, includes rails 270 that are configured to ride on the guide rails 170 of the P-Pod 100. Spring plungers 220 are mounted on two of the rails 270, and serve to separate the CubeSats during deployment when there are multiple CubeSats within the P-Pod. Switches 230 are mounted on the remaining two rails 270, and serve to signal that the CubeSat has been deployed.
The regions 210 between the rails 270 are illustrated as plane surfaces, but will typically include components of the CubeSat 200, such as solar panels, deployable antennas, sensing instruments, and the like. The surfaces 210 merely identify the maximum extent that such components may occupy. Because the P-Pod 100 provides a sealed enclosure, the components of the CubeSat 200 need not be enclosed. Depending upon the arrangement of components within the CubeSat 200, an access panel 240 may be provided on either or both sides of the CubeSat 200, corresponding to the access panels 130 of the P-Pod 100.
The ISIPOD device includes features similar to the P-Pod 100.
Although the P-Pod and ISIPOD devices are relatively efficient and reliable, some of their features may be considered ‘sub-optimal’.
For example, the requirement to provide four rails 270 on the CubeSat 200 requires the external profile of the CubeSat to be rectangular. Additionally, because the CubeSat 200 must ride the guide rails 170, there must be a gap between the extent of the rails 270 of the CubeSat 200 and the distance between the guide rails 170 of the P-Pod. Although the gap may be slight (about 0.5 mm), it allows the CubeSat 200 to vibrate within the P-Pod 100 during transport and launch, which has damaging potential and is very difficult to analytically model.
In like manner, because the guide rails 170 of the P-Pod 100 are the only surfaces that the CubeSat 200 may contact, and this contact must be via the rails 270 of the CubeSat 200, the CubeSat 200 cannot rely on the P-Pod 100 for providing other support surfaces that might simplify the mechanical design of particular CubeSats 200.
The arrangement of the release mechanism 120 above the door 110 limits the options for mounting the P-Pod 100 in the delivery spacecraft, particularly when multiple P-Pods are included in the delivery spacecraft.
The use of a coil spring 160 results in a non-uniform force being applied to the push-plate 150 as the spring 160 expands; it may also introduce an undesired torquing force, which could introduce a spin to the CubeSat as it is released.
It would be advantageous to provide a canisterized satellite dispenser that overcomes one or more of the sub-optimal features of conventional canisterized satellite dispenser, such as P-Pod and ISIPOD. It would be advantageous to provide a canisterized satellite dispenser that has one or more of the following features: fewer than four guiderails, preloaded contact with the satellite, a rectangular profile in each dimension, a dispensing mechanism that does not use a coil spring, and an inner profile that allows further supporting contact with the canisterized satellite.
These advantages, and others, can be realized by a canisterized satellite dispenser that includes one or more of: a pair of guide channels that eliminate the requirement of a rectangular profile for the satellite; a preload system that secures the canisterized satellite during transport and launch, and releases to dispense the canisterized satellite; a constant-force spring to provide a uniform and predictable dispensing force; an external rectangular profile in each dimension; and internal support surfaces that simplify the design of canisterized satellites, particularly those with deployable components. Each canisterized satellite includes a pair of opposing flanges on a lower portion of the satellite that ride in a channel formed by the dispenser's guide rails and restraining flanges; no other support constraints are imposed. During travel and launch, the satellite flanges are held against the restraining flanges, rigidly fixing the satellite to the dispenser until the satellite is deployed.
Throughout the drawings, the same reference numerals indicate similar or corresponding features or functions. The drawings are included for illustrative purposes and are not intended to limit the scope of the invention.